Sessions and sub directories

I curently have sessions working fine within the directory in which I start them... but I need them to be still active when I move down a directory. What I have is a directory of pages for a user and a sub direcory eg /administrator/ with the maintenence pages. When a autherised user logs in the session data is stored with the user name and pass and they are displayed with a linkt to the file /administrator/default.php when the page is run it again checks for autherisation rights on the session data ....but It no loger exists and they are "header'd" back down to the general users area where the session data is again found. I'm guessing this has to do with the way the cookies are set when sent but I do not have access to the ISP to reconfigure thier php.ini files or any thing. Any help apreciated. JAmie